Redshift. You see, whenever an atom or molecule emits light, it gives off that light at a very few particular wavelengths. For instance, if you have hydrogen, you'll always get light at wavelengths of 656 nanometers (red), 486 nm (cyan), 434 nm (indigo), 410 nm (violet), and 397 nm (on the border of violet/ultraviolet):

Now there are three things -- and only three things (unless you really want to get technical) -- that can happen to this light to change the wavelengths that you see. Let's go over what they are.

1. Gravitational Redshift. If you're deep in a gravitational field (like close to a black hole), you have to use up energy to climb out of it. For light of all types, energy and wavelength are very closely related to each other. Smaller wavelength = higher energy and larger wavelength = lower energy, so if you need to climb out of a strong gravitational field, you lose energy, and therefore your light gets shifted towards the red. This is what we call redshift, where something happens to make the wavelength of your light longer and lower in energy. But gravitational redshift is rarely significant; two other effects are far more important.

2. Redshift due to motion. If an object that emits light moves away from you, the light from it gets redshifted. This is the same exact effect -- the doppler shift -- that causes police sirens to sound lower pitched when they move away from you. One thing that's neat? If a light-emitting object moves towards you, the light gets blue-shifted, and becomes more energetic! (We see this happening for the Andromeda galaxy, one of the only ones in the Universe that moves towards us.) And although this is incredibly useful, this is not what's happening to light in the Universe. Remember, I told you that these distant galaxies aren't moving, the space between them is just expanding. Well, guess what?

3. Expanding space causes a redshift! (And thanks to av8n.com for the image!) You see, as space expands (above), the wavelengths of the light in it also expand, as you can see below.

And this last effect is so important for the expanding Universe. Why? Well, if we measure the light from many, many distant objects and determine their distances, we can -- simply based on the objects' redshifts -- learn the entire history of how the Universe expanded. The redshift isn't hard to measure, either:

It is from literally millions and millions of these individual measurements that we've been able to determine the entire history of how the Universe expanded. That, among other things, is how we discovered dark energy and the accelerating Universe! Pretty remarkable stuff, and yet, not intuitive at all.

So what should you take away from this? That as light travels through space and space expands, it causes the wavelength of that very light to expand, too. And that's how we learn about the history of cosmic expansion in our Universe. Again, it's expansion that's causing this redshift, and not motion. Hope this helps shed some light on some of the most confusing stuff out there!

MUFON

Stabilize the camera on a tripod. If there is no tripod, then set it on top of a stable, flat surface. If that is not possible lean against a wall to stabilize your body and prevent the camera from filming in a shaky, unsteady manner.

Provide visual reference points for comparison. This includes the horizon, treetops, lampposts, houses, and geographical landmarks (i.e., Horsetooth Reservoir, Mt. Adams, etc.) Provide this in the video whenever is appropriate and doesn’t detract from what your focus is, the UFO.

Narrate your videotape. Provide details of the date, time, location, and direction (N,S,E,W) you are looking in. Provide your observations on the weather, including approximate temperature, windspeed, any visible cloud cover or noticeable weather anomalies or events. Narrate on the shape, size, color, movements, approximate altitude of the UFO, etc and what it appears to be doing. Also include any unusual physical, psychological or emotional sensations you might have. Narrate any visual reference points on camera so they correlate with what the viewer will see, and thereby will be better able to understand.

Be persistent and consistent. Return to the scene to videotape and record at this same location. If you have been successful once, the UFO sightings may be occurring in this region regularly, perhaps for specific reasons unknown, and you may be successful again. You may also wish to return to the same location at a different time of day (daylight hours) for better orientation and reference. Film just a minute or two under “normal” circumstances for comparison. Write down what you remember immediately after. As soon as you are done recording the experience/event, immediately write down your impressions, memories, thoughts, emotions, etc. so it is on the record in writing. If there were other witnesses, have them independently record their own impressions, thoughts, etc. Include in this exercise any drawings, sketches, or diagrams. Make sure you date and sign your documentation.

Always be prepared. Have a digital camera or better yet a video camera with you, charged and ready to go, at all times. Make sure you know how to use your camera (and your cell phone video/photo camera) quickly and properly. These events can occur suddenly, unexpectedly, and often quite randomly, so you will need to be prepared.